Lithium iron phosphate (LFP) battery cells are ubiquitous in electric vehicles and stationary energy storage because they are cheap and have a long lifetime. This work compares LFP/graphite pouch cells undergoing charge-discharge cycles over five state of charge (SOC) windows (0%–25%, 0%–60%, 0%–80%, 0%–100%, and 75%–100%). Cycling LFP cells across a lower average SOC results in less capacity fade than cycling across a higher average SOC, regardless of depth of discharge. The primary capacity fade mechanism is lithium inventory loss due to: lithiated graphite reactivity with electrolyte, which increases incrementally with SOC, and lithium alkoxide species causing iron dissolution and deposition on the negative electrode at high SOC which further accelerates lithium inventory loss. Our results show that even low voltage LFP systems (3.65 V) have a tradeoff between average SOC and lifetime. Operating LFP cells at lower average SOC can extend their lifetime substantially in both EV and grid storage applications.
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JES is the flagship journal of The Electrochemical Society. Published continuously from 1902 to the present, JES remains one of the most highly-cited journals in electrochemistry and solid-state science and technology.
Eniko S. Zsoldos et al 2024 J. Electrochem. Soc. 171 080527
Peter Keil et al 2016 J. Electrochem. Soc. 163 A1872
In this study, the calendar aging of lithium-ion batteries is investigated at different temperatures for 16 states of charge (SoCs) from 0 to 100%. Three types of 18650 lithium-ion cells, containing different cathode materials, have been examined. Our study demonstrates that calendar aging does not increase steadily with the SoC. Instead, plateau regions, covering SoC intervals of more than 20%–30% of the cell capacity, are observed wherein the capacity fade is similar. Differential voltage analyses confirm that the capacity fade is mainly caused by a shift in the electrode balancing. Furthermore, our study reveals the high impact of the graphite electrode on calendar aging. Lower anode potentials, which aggravate electrolyte reduction and thus promote solid electrolyte interphase growth, have been identified as the main driver of capacity fade during storage. In the high SoC regime where the graphite anode is lithiated more than 50%, the low anode potential accelerates the loss of cyclable lithium, which in turn distorts the electrode balancing. Aging mechanisms induced by high cell potential, such as electrolyte oxidation or transition-metal dissolution, seem to play only a minor role. To maximize battery life, high storage SoCs corresponding to low anode potential should be avoided.
Manuel Ank et al 2023 J. Electrochem. Soc. 170 120536
Battery research depends upon up-to-date information on the cell characteristics found in current electric vehicles, which is exacerbated by the deployment of novel formats and architectures. This necessitates open access to cell characterization data. Therefore, this study examines the architecture and performance of first-generation Tesla 4680 cells in detail, both by electrical characterization and thermal investigations at cell-level and by disassembling one cell down to the material level including a three-electrode analysis. The cell teardown reveals the complex cell architecture with electrode disks of hexagonal symmetry as well as an electrode winding consisting of a double-sided and homogeneously coated cathode and anode, two separators and no mandrel. A solvent-free anode fabrication and coating process can be derived. Energy-dispersive X-ray spectroscopy as well as differential voltage, incremental capacity and three-electrode analysis confirm a NMC811 cathode and a pure graphite anode without silicon. On cell-level, energy densities of 622.4 Wh/L and 232.5 Wh/kg were determined while characteristic state-of-charge dependencies regarding resistance and impedance behavior are revealed using hybrid pulse power characterization and electrochemical impedance spectroscopy. A comparatively high surface temperature of ∼70 °C is observed when charging at 2C without active cooling. All measurement data of this characterization study are provided as open source.
Jorn M. Reniers et al 2019 J. Electrochem. Soc. 166 A3189
The maximum energy that lithium-ion batteries can store decreases as they are used because of various irreversible degradation mechanisms. Many models of degradation have been proposed in the literature, sometimes with a small experimental data set for validation. However, a comprehensive comparison between different model predictions is lacking, making it difficult to select modelling approaches which can explain the degradation trends actually observed from data. Here, various degradation models from literature are implemented within a single particle model framework and their behavior is compared. It is shown that many different models can be fitted to a small experimental data set. The interactions between different models are simulated, showing how some of the models accelerate degradation in other models, altering the overall degradation trend. The effects of operating conditions on the various degradation models is simulated. This identifies which models are enhanced by which operating conditions and might therefore explain specific degradation trends observed in data. Finally, it is shown how a combination of different models is needed to capture different degradation trends observed in a large experimental data set. Vice versa, only a large data set enables to properly select the models which best explain the observed degradation.
Weilong Ai et al 2020 J. Electrochem. Soc. 167 013512
Whilst extensive research has been conducted on the effects of temperature in lithium-ion batteries, mechanical effects have not received as much attention despite their importance. In this work, the stress response in electrode particles is investigated through a pseudo-2D model with mechanically coupled diffusion physics. This model can predict the voltage, temperature and thickness change for a lithium cobalt oxide-graphite pouch cell agreeing well with experimental results. Simulations show that the stress level is overestimated by up to 50% using the standard pseudo-2D model (without stress enhanced diffusion), and stresses can accelerate the diffusion in solid phases and increase the discharge cell capacity by 5.4%. The evolution of stresses inside electrode particles and the stress inhomogeneity through the battery electrode have been illustrated. The stress level is determined by the gradients of lithium concentration, and large stresses are generated at the electrode-separator interface when high C-rates are applied, e.g. fast charging. The results can explain the experimental results of particle fragmentation close to the separator and provide novel insights to understand the local aging behaviors of battery cells and to inform improved battery control algorithms for longer lifetimes.
Yuliya Preger et al 2020 J. Electrochem. Soc. 167 120532
Energy storage systems with Li-ion batteries are increasingly deployed to maintain a robust and resilient grid and facilitate the integration of renewable energy resources. However, appropriate selection of cells for different applications is difficult due to limited public data comparing the most commonly used off-the-shelf Li-ion chemistries under the same operating conditions. This article details a multi-year cycling study of commercial LiFePO4 (LFP), LiNixCoyAl1−x−yO2 (NCA), and LiNixMnyCo1−x−yO2 (NMC) cells, varying the discharge rate, depth of discharge (DOD), and environment temperature. The capacity and discharge energy retention, as well as the round-trip efficiency, were compared. Even when operated within manufacturer specifications, the range of cycling conditions had a profound effect on cell degradation, with time to reach 80% capacity varying by thousands of hours and cycle counts among cells of each chemistry. The degradation of cells in this study was compared to that of similar cells in previous studies to identify universal trends and to provide a standard deviation for performance. All cycling files have been made publicly available at batteryarchive.org, a recently developed repository for visualization and comparison of battery data, to facilitate future experimental and modeling efforts.
Kevin N. Wood et al 2024 J. Electrochem. Soc. 171 080501
Gaining insights into the fundamental properties of lithium-ion batteries through scalable and non-destructive methods is challenging for commercial cell formats. In this work, a simple analytical pulsing protocol (APP) is performed on a commercial cell to understand its thermodynamic, kinetic, and mass transport properties. While testing procedures that rely on electrochemical pulses are well documented, the APP is novel in the level of fundamental insight that can be gained. For thermodynamics, a static-differential capacity analysis can be performed that removes the effects of kinetic and transport overpotentials and allows for the calculation of Gibbs free energy. For kinetics, the exchange current density of the cell can be calculated according to the Butler-Volmer model. For transport, a whole-cell lithium-ion diffusion coefficient can be calculated from a derivation of Fick's second law and the generalized flux equation. Comparing the results from these properties gives an unparalleled level of mechanistic insight into battery performance from a single non-destructive technique. This APP requires no additional equipment and provides properties that can be easily correlated to materials or processing parameters. Therefore, the APP is valuable for research and development, manufacturing, quality assurance, and second-life applications, among others.
Francois L. E. Usseglio-Viretta et al 2018 J. Electrochem. Soc. 165 A3403
Battery performance is strongly correlated with electrode microstructural properties. Of the relevant properties, the tortuosity factor of the electrolyte transport paths through microstructure pores is important as it limits battery maximum charge/discharge rate, particularly for energy-dense thick electrodes. Tortuosity factor however, is difficult to precisely measure, and thus its estimation has been debated frequently in the literature. Herein, three independent approaches have been applied to quantify the tortuosity factor of lithium-ion battery electrodes. The first approach is a microstructure model based on three-dimensional geometries from X-ray computed tomography (CT) and stochastic reconstructions enhanced with computationally generated carbon/binder domain (CBD), as CT is often unable to resolve the CBD. The second approach uses a macro-homogeneous model to fit electrochemical data at several rates, providing a separate estimation of the tortuosity factor. The third approach experimentally measures tortuosity factor via symmetric cells employing a blocking electrolyte. Comparisons have been made across the three approaches for 14 graphite and nickel-manganese-cobalt oxide electrodes. Analysis suggests that if the tortuosity factor were characterized based on the active material skeleton only, the actual tortuosities would be 1.35–1.81 times higher for calendered electrodes. Correlations are provided for varying porosity, CBD phase interfacial arrangement and solid particle morphology.
George E. Blomgren 2017 J. Electrochem. Soc. 164 A5019
This year, the battery industry celebrates the 25th anniversary of the introduction of the lithium ion rechargeable battery by Sony Corporation. The discovery of the system dates back to earlier work by Asahi Kasei in Japan, which used a combination of lower temperature carbons for the negative electrode to prevent solvent degradation and lithium cobalt dioxide modified somewhat from Goodenough's earlier work. The development by Sony was carried out within a few years by bringing together technology in film coating from their magnetic tape division and electrochemical technology from their battery division. The past 25 years has shown rapid growth in the sales and in the benefits of lithium ion in comparison to all the earlier rechargeable battery systems. Recent work on new materials shows that there is a good likelihood that the lithium ion battery will continue to improve in cost, energy, safety and power capability and will be a formidable competitor for some years to come.
Philip Minnmann et al 2024 J. Electrochem. Soc. 171 060514
The kinetics of composite cathodes for solid-state batteries (SSBs) relies heavily on their microstructure. Spatial distribution of the different phases, porosity, interface areas, and tortuosity factors are important descriptors that need accurate quantification for models to predict the electrochemistry and mechanics of SSBs. In this study, high-resolution focused ion beam-scanning electron microscopy tomography was used to investigate the microstructure of cathodes composed of a nickel-rich cathode active material (NCM) and a thiophosphate-based inorganic solid electrolyte (ISE). The influence of the ISE particle size on the microstructure of the cathode was visualized by 3D reconstruction and charge transport simulation. By comparison of experimentally determined and simulated conductivities of composite cathodes with different ISE particle sizes, the electrode charge transport kinetics is evaluated. Porosity is shown to have a major influence on the cell kinetics and the evaluation of the active mass of electrochemically active particles reveals a higher fraction of connected NCM particles in electrode composites utilizing smaller ISE particles. The results highlight the importance of homogeneous and optimized microstructures for high performance SSBs, securing fast ion and electron transport.
Dawei Xia et al 2024 J. Electrochem. Soc. 171 099001
Kaviya Murugan et al 2024 J. Electrochem. Soc. 171 097503
The burgeoning intersection of machine learning (ML) with electrochemical sensing heralds a transformative era in analytical science, pushing the boundaries of what's possible in detecting and quantifying chemical substances with unprecedented precision and efficiency. This convergence has accelerated a number of discoveries, improving electrochemical sensors' sensitivity, selectivity, and ability to comprehend complicated data streams in real-time. Such advancements are crucial across various applications, from monitoring health biomarkers to detecting environmental pollutants and ensuring industrial safety. Yet, this integration is not without its challenges; it necessitates navigating intricate ethical considerations around data use, ensuring robust data privacy measures, and developing specialized software tools that balance accessibility and security. As the field progresses, addressing these challenges head-on is essential for harnessing the full potential of ML-enhanced electrochemical sensing. This review briefly explores these dimensions, spotlighting the significant technological strides, the ethical landscape, and the dynamic interplay between open-source and proprietary software solutions while also casting a forward gaze at the promising future directions of this interdisciplinary venture.
Fareeha Marriam et al 2024 J. Electrochem. Soc. 171 096501
The superior kinetics of charge carriers and greater visible light absorption are important factors for enhancing photoelectrochemical performance. Herein, the core–shell heterostructure has been developed by encapsulating single-phase MnZnO3 over TiO2 nanotubes by aerosol-assisted chemical vapor deposition approach. The fabricated photoanodes have been characterized by employing various techniques including X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, and photoluminescence. Moreover, the mechanism for electron/hole transfer has been focused by a brief electrochemical investigation. The bilayer 1D/2D TiO2@MnZnO3 photoanode exhibited higher current density (2 mA cm−2) as compared to pristine TiO2-nanotubes (0.174 mA cm−2) at 1.52 V vs RHE. The superior photoactivity of heterostructure is attributed to the rapid transfer of photogenerated charge carriers via the Type-II mechanism. Furthermore, the reduced band gap (2.05 eV) accounts for good absorption in the visible region of light, while the interfacial electric field allowed the improved charge separation. The synergistic strategy in the present work demonstrates the promising significance of a heterojunction interface to optimize photovoltaic devices.
Chao Zhang et al 2024 J. Electrochem. Soc. 171 090506
The thermal safety of lithium-ion batteries has garnered significant attention due to its pivotal role in the field of new energy. In this work, a three-dimensional electrochemical-thermal coupling model based on the P2D model was established for predicting the thermal performance. The charge-discharge and temperature rise experiments via 18650 cylindrical Li[Ni0.6Co0.2Mn0.2]O2 / graphite batteries are designed to confirm the rationality of the model. The simulation results show that the highest temperature of the battery surface during discharging at 1 C and 4 C are 42.85 °C and 61.25 °C, and the experimental results are 42.50 °C and 62.85 °C, respectively. The electrode heat generation mainly comes from the reaction heat of cathode and anode during 1 C charge process, the maximum power is 1.2 W and 0.6 W, respectively. In the discharge process, the cathode dominates the reaction contribution of 1.02 W and the reaction heat power from the anode is only 0.016 W. The capacity of heat dissipation can be increased by enhancing the convective heat transfer coefficient and air velocity within a reasonable range. The proposed electrochemical-thermal coupling model is valuable to evaluate the heat behavior and promote the battery development.
Farah En-Nakra et al 2024 J. Electrochem. Soc. 171 097502
In this study, we developed a facile and low-cost method to prepare a modified electrode by coating the pencil graphite electrode (PGE) surface with 8-nitroquinoline (8-NQ). The surface modification process was carried out by electrochemical reduction of 8-NQ on the PGE surface in ethanol solution. The optimum conditions were determined for the experimental studies. The differential pulse voltammetry was used to determine rutin with the modified electrode (8-NQ/PGE). The developed electrode showed excellent performance for rutin oxidation in a pH 3.0 Britton Robinson buffer (BR). In this media, linearly increasing anodic peak currents were observed with the concentration of rutin in two wide concentration ranges (i.e., 0.016–0.96 μM and 0.96‒19.73 μM), the sensor showed a low detection limit (i.e., 4.14 nM) (3 s m−1). It displayed good stability and selectivity. Also, it was used successfully for the determination of rutin in orange juice samples.
Highlights:
An 8-nitroquinoline coated pencil graphite surface for rutin.
High conductive surface with a good stability and reproducibility.
An extensive linear range with a low detection limit of 4.14 nM (3 s m−1).
Kaviya Murugan et al 2024 J. Electrochem. Soc. 171 097503
The burgeoning intersection of machine learning (ML) with electrochemical sensing heralds a transformative era in analytical science, pushing the boundaries of what's possible in detecting and quantifying chemical substances with unprecedented precision and efficiency. This convergence has accelerated a number of discoveries, improving electrochemical sensors' sensitivity, selectivity, and ability to comprehend complicated data streams in real-time. Such advancements are crucial across various applications, from monitoring health biomarkers to detecting environmental pollutants and ensuring industrial safety. Yet, this integration is not without its challenges; it necessitates navigating intricate ethical considerations around data use, ensuring robust data privacy measures, and developing specialized software tools that balance accessibility and security. As the field progresses, addressing these challenges head-on is essential for harnessing the full potential of ML-enhanced electrochemical sensing. This review briefly explores these dimensions, spotlighting the significant technological strides, the ethical landscape, and the dynamic interplay between open-source and proprietary software solutions while also casting a forward gaze at the promising future directions of this interdisciplinary venture.
Samaneh Shahsavarifar et al 2024 J. Electrochem. Soc. 171 080536
Polyoxometalates (POMs) are inorganic nanoclusters that consist of oxygen and transition metals. These nanoclusters serve as excellent precursors for creating electrode materials that contain transition metals. Additionally, the interaction between POMs and carbon substrates produces positive synergistic effects. There has been considerable attention on employing POMs and carbon nanostructures (for example carbon nanotubes, graphene, and mesoporous carbon) in composite materials for diverse purposes including catalysis, transformation, storage of energy, molecular detection, and electrical detection. By combining the reactive nature of POMs with the exceptional electrical properties of carbon nanostructures, highly desirable composite features can be achieved. This review delves into the extensive use of POM/nanocarbon materials for constructing rechargeable lithium-ion batteries, providing an in-depth analysis of the characteristics of POMs and the techniques employed for binding carbon.
Jin Zhang et al 2024 J. Electrochem. Soc. 171 082502
Titanium (Ti), a metal known for its exceptional performance, is abundant in nature and holds significant potential for a variety of applications and advancements. However, the conventional Kroll process has faced criticism due to its high energy consumption, complex procedures, and environmental impact. In response, metallurgists worldwide are actively exploring innovative and sustainable methods for Ti production. Titanium metal production is generally classified into two main methods according to the specific raw materials and preparation methods employed: thermal reduction and molten-salt electrolysis. This paper provides a review of these two primary Ti production processes, comparing their respective advantages and suggesting potential areas for improvement and breakthroughs. In particular, we emphasize recent advancements in molten-salt electrolysis, such as the utilization of Ti-rich alloys as raw materials and liquid metals as cathodes. Notably, the advances in molten-salt electrolysis with liquid metal as cathodes show promise for the continuous production of high-purity Ti at reduced costs and energy consumption. We also introduce a novel approach: the preparation of Ti metal through double-chamber molten-salt electrolysis. Additionally, we explore future directions for enhancing the Ti metal production process.
Highlights
Future directions for green and sustainable titanium metal production.
Comparison of thermal reduction and molten salt electrolysis methods.
Latest advancements in molten salt electrolysis for titanium production.
Introduction of double-chamber molten salt electrolysis for titanium metal preparation.
Neha Sharma et al 2024 J. Electrochem. Soc. 171 087507
Gas sensing technology has evolved over the last 50 years but there has been a lacuna to understand the sensing mechanism. The understanding becomes even more complicated when gases like Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX) are sensed using conventional gas sensors. BTEX gases have inert chemical behaviour, making it difficult to detect such gases using the widely explored metal-oxide-semiconductors (MOS). BTEX gases are generated in petroleum and other industries and hence their detection at low ppm is a necessity as it is carcinogenic in nature and possesses a threat to human health. For efficient sensing of such gases, a variety of materials including quantum dots, nano-flakes of different geometry, carbon-based materials etc. are being explored. This review focuses on the different materials and their properties which makes them efficient sensors to detect BTEX gases. Polymer-based materials are out of the scope of this review article as the topic deserves a separate article because of its vastness. In future scope, probable materials which can prove to be a good BTEX gas sensor are discussed.
Shivani Saklani et al 2024 J. Electrochem. Soc. 171 087502
Zoonotic diseases are a pressing challenge to global health, arising from their interspecies transmission and potential for pandemics. Conventional diagnostic methodologies often suffer from limitations in speed, sensitivity, and accuracy, underscoring the imperative for innovative solutions. Nanomaterial-integrated biosensors, especially in electrochemical modules, have gained increasing attention as promising tools for the rapid, sensitive, point-of-care and targeted detection of zoonotic pathogens. Despite considerable progress, pervasive challenges, including market fragmentation and research disparities, impede widespread adoption. This review explores the essential role of electrochemical biosensors in combating zoonotic diseases, underscoring the urgency for accessible, cost-effective, and high-throughput diagnostic platforms. It details the principles of electrochemical biosensing and highlights the role of diversified nanomaterials in enhancing the performance of biosensors. Furthermore, it examines the integration of nanomaterials with different electrodes and signal amplification strategies to improve its sensing performance. It details the current challenges, alternate solutions and perspectives in developing and translating these biosensors for point-of-care diagnosis/surveillance of zoonotic diseases. This review provides valuable insights into the potential of nanomaterial-based electrochemical biosensors to revolutionize the diagnosis and management of zoonotic diseases, ultimately contributing to global efforts to mitigate the impact of these contagious threats on human and animal health.
Philip Minnmann et al 2024 J. Electrochem. Soc. 171 060514
The kinetics of composite cathodes for solid-state batteries (SSBs) relies heavily on their microstructure. Spatial distribution of the different phases, porosity, interface areas, and tortuosity factors are important descriptors that need accurate quantification for models to predict the electrochemistry and mechanics of SSBs. In this study, high-resolution focused ion beam-scanning electron microscopy tomography was used to investigate the microstructure of cathodes composed of a nickel-rich cathode active material (NCM) and a thiophosphate-based inorganic solid electrolyte (ISE). The influence of the ISE particle size on the microstructure of the cathode was visualized by 3D reconstruction and charge transport simulation. By comparison of experimentally determined and simulated conductivities of composite cathodes with different ISE particle sizes, the electrode charge transport kinetics is evaluated. Porosity is shown to have a major influence on the cell kinetics and the evaluation of the active mass of electrochemically active particles reveals a higher fraction of connected NCM particles in electrode composites utilizing smaller ISE particles. The results highlight the importance of homogeneous and optimized microstructures for high performance SSBs, securing fast ion and electron transport.
S. Yanev et al 2024 J. Electrochem. Soc. 171 020512
Li-In electrodes are widely applied as counter electrodes in fundamental research on Li-metal all-solid-state batteries. It is commonly assumed that the Li-In anode is not rate limiting, i.e. the measurement results are expected to be representative of the investigated electrode of interest. However, this assumption is rarely verified, and some counterexamples were recently demonstrated in literature. Herein, we fabricate Li-In anodes in three different ways and systematically evaluate the electrochemical properties in two- and three-electrode half-cells. The most common method of pressing Li and In metal sheets together during cell assembly resulted in poor homogeneity and low rate performance, which may result in data misinterpretation when applied for investigations on cathodic phenomena. The formation of a Li-poor region on the separator side of the anode is identified as a major kinetic bottleneck. An alternative fabrication of a Li-In powder anode resulted in no kinetic benefits. In contrast, preparing a composite from Li-In powder and sulfide electrolyte powder alleviated the kinetic limitation, resulted in superior rate performance, and minimized the impedance. The results emphasize the need to fabricate optimized Li-In anodes to ensure suitability as a counter electrode in solid-state cells.
Highlights
The fabrication of Li-In anodes needs to be optimized to ensure suitability as a counter electrode in sulfide all-solid-state batteries.
The Li-In counter electrode may often be the limiting factor of sulfide all-solid-state halfcells.
Pressing Li and In foil together results in a kinetically limited anode.
Composites from Li-In and sulfide electrolyte result in stable reference potential, superior rate performance and low impedance of the counter electrode.
Ramver Singh et al 2024 J. Electrochem. Soc. 171 013501
Electrical discharge micromachining (EDM) poses challenges to the fatigue-life performance of machined surfaces due to thermal damage, including recast layers, heat-affected zones, residual stress, micro-cracks, and pores. Existing literature proposes various ex situ post-processing techniques to mitigate these effects, albeit requiring separate facilities, leading to increased time and costs. This research involves an in situ sequential electrochemical post-processing (ECPP) technique to enhance the quality of EDMed micro-holes on titanium. The study develops an understanding of the evolution of overcutting during ECPP, conducting unique experiments that involve adjusting the initial radial interelectrode gap (utilizing in situ wire-electrical discharge grinding) and applied voltage. Additionally, an experimentally validated transient finite element method (FEM) model is developed, incorporating the passive film formation phenomenon for improved accuracy. Compared to EDM alone, the sequential EDM-ECPP approach produced micro-holes with superior surface integrity and form accuracy, completely eliminating thermal damage. Notably, surface roughness (Sa) was reduced by 80% after the ECPP. Increasing the voltage from 8 to 16 V or decreasing the gap from 60 to 20 μm rendered a larger overcut. This research's novelty lies in using a two-phase dielectric (water-air), effectively addressing dielectric and electrolyte cross-contamination issues, rendering it suitable for commercial applications.
Highlights
Better micro-hole quality through in situ sequential eco-friendly near-dry EDM & ECM
Successfully resolved dielectric-electrolyte cross-contamination in sequential processes
Unique experiments that adjust the initial radial IEG using in situ wire-EDG
Developed and validated a transient FEM model, incorporating passivation aspect
Achieved recast layer-free holes with Sa values approximately 80% lower than EDM holes
D. A. Sudarikov et al 2023 J. Electrochem. Soc. 170 086505
Vanadium dioxide is widely known for its metal-insulator transition (MIT), in which drastic changes in resistivity and IR-transparency occur. This makes VO2 thin films promising materials for high-frequency optoelectronic devices. To get the most MIT sharpness, thin films should not contain impurities of hyper-oxygen or hypo-oxygen phases arising during VO2 synthesis. To ascertain the conditions of single-phase VO2 existence, the equilibrium boundaries of VO2 with neighboring phases were determined using the electromotive force method (EMF) with a solid electrolyte ZrO2(Y2O3). Our data for the high-oxygen boundary of VO2 existence in equilibrium with the V6O13 phase agree with the only data known in the literature. We established that VO2 is, in equilibrium with the V9O17 phase at the low-oxygen boundary, which forms V8O15 under further reduction. The temperature of the peritectoid decomposition of V9O17 is established, and the corresponding corrections to the phase diagram of the vanadium-oxygen system are introduced. The Gibbs energies for V9O17, V8O15, and V6O13 formation reactions are calculated. It is also shown that the IR reflectance of VO2 films brought to equilibrium at the high-oxygen boundary is much greater than that of films equilibrated at the low-oxygen boundary.
Highlights
Equilibrium boundaries of VO2 phase stability were studied by the EMF method.
Low-oxygen boundary revealed more complex equilibriums than previously assumed.
Thermodynamic data about equilibriums of V8O15, V9O17, VO2, V6O13 were obtained.
New information was added to the phase diagram of the vanadium-oxygen system.
Influence of nonstoicometry on MIT was shown by IR experiments with thin VO2 films.
Runze Zhang et al 2023 J. Electrochem. Soc. 170 086502
Electrochemical Impedance Spectroscopy (EIS) is a powerful tool for electrochemical analysis; however, its data can be challenging to interpret. Here, we introduce a new open-source tool named AutoEIS that assists EIS analysis by automatically proposing statistically plausible equivalent circuit models (ECMs). AutoEIS does this without requiring an exhaustive mechanistic understanding of the electrochemical systems. We demonstrate the generalizability of AutoEIS by using it to analyze EIS datasets from three distinct electrochemical systems, including thin-film oxygen evolution reaction (OER) electrocatalysis, corrosion of self-healing multi-principal components alloys, and a carbon dioxide reduction electrolyzer device. In each case, AutoEIS identified competitive or in some cases superior ECMs to those recommended by experts and provided statistical indicators of the preferred solution. The results demonstrated AutoEIS's capability to facilitate EIS analysis without expert labels while diminishing user bias in a high-throughput manner. AutoEIS provides a generalized automated approach to facilitate EIS analysis spanning a broad suite of electrochemical applications with minimal prior knowledge of the system required. This tool holds great potential in improving the efficiency, accuracy, and ease of EIS analysis and thus creates an avenue to the widespread use of EIS in accelerating the development of new electrochemical materials and devices.
Highlights
A novel tool that automatically generates candidate ECMs for EIS analysis without training data
Generalizable across various electrochemical systems
Minimized human bias and expert knowledge requirements
Reproducible ECM exploration with explicit, measurable, and traceable biases
High-throughput EIS analysis to accelerate electrochemical materials research
Karger et al
Degradation models are important tools for understanding and mitigating lithium-ion battery aging, yet a universal model that can predict degradation under all operating conditions remains elusive. One challenge is the coupled influence of calendar and cycle aging phases on degradation mechanisms, such as solid electrolyte interphase (SEI) formation. In this work, we identify and systematically compare three different SEI interaction theories found in the literature, and apply them to experimental degradation data from a commercial lithium-ion cell. In a step-by-step process, and after careful data selection, we show that SEI delamination without any cracking of the active particles, and SEI microcracking, where cycling only affects SEI growth during the cycle itself, are both unlikely candidates. Instead, the results indicate that upon cycling, both the SEI and the active particle crack, and we provide a simple, 4-parameter equation that can predict the particle crack rate. Contrary to the widely-accepted Paris’ law, the particle crack rate decreases with increasing cycles, potentially due to changing intercalation dynamics resulting from the increasing surface-to-volume ratio of the active particles. The proposed model predicts SEI formation accurately at different storage conditions, while simply adding the degradation from pure calendar and cycle aging underestimates the total degradation.
Jun et al
It is desirable to develop solid electrolytes that have both excellent reductive stability against lithium metal and oxidative stability against high-voltage cathodes. However, no inorganic superionic conductors reported thus far satisfy these criteria. Nitrides exhibit intrinsically superior stability against reduction but are often readily oxidized at voltages as low as 0.6 V. In this article, we investigated all nitride-based compounds to search for materials with improved oxidative stabilities over 2.0 V while retaining their intrinsic stability against Li metal. We found two compounds, LiPN2 and Li2CN2, with high oxidative stability > 2.0 V and low vacancy migration energies. Using fine-tuned CHGNet machine-learning interatomic potential, we found that upon introducing aliovalent dopants to introduce vacancies in Li2CN2, the dopant and vacancy strongly anchor with each other to result in trapped vacancies, which lowers ionic conductivity. In contrast, vacancies and dopants have minimal interactions in LiPN2, resulting in a high ionic conductivity. These two compounds were synthesized, but their ionic conductivities were not successfully measured because of the challenges in densification. With improved processing conditions, these compounds may serve as anode-side separators in dual-separator-type all-solid-state batteries or anode buffer layer materials interfaced with lithium metal.
Schmidt et al
A novel approach is presented to model delamination and recontacting at internal interfaces of three-dimensional resolved microstructures of solid-state batteries. To resolve the effect of delaminations, we incorporate the consistent enforcement of contact constraints at those interfaces using Nitsche's method. The model incorporates charge, mass, and momentum conservation to consider electrochemistry, solid mechanics, and their interaction. After introducing and verifying the model, we examine various scenarios to quantify the effect of delaminations at the electrode-solid electrolyte interface on cell performance. The simulations show that increased mechanical prestress mitigates delamination tendencies at the electrode-solid electrolyte interface. Consistent with existing literature, the simulations demonstrate that delaminations increase the internal resistance and reduce the amount of transferred charge. In contrast to experimental analyses, the presented model allows quantitative and in-depth investigations of delamination effects. Furthermore, our analysis of two cell concepts - one assembled in the discharged state and another assembled in the charged state - indicates that cells assembled in the discharged state show a higher delamination risk at the electrode-solid electrolyte interface. The study highlights the critical relationship between solid mechanics and electrochemistry in consideration of delamination phenomena in solid-state batteries, offering valuable insights for optimizing battery design and performance.
Kim et al
Safety and maintaining high performance are key considerations during the operation of lithium-ion batteries. Battery degradation, in particular lithium plating and loss of active material, is often accelerated by fast charging. This study explores a strategy for the design of fast charging protocols that takes into account the influence of the variability between battery cells on factors that can impact degradation. We employ a non-intrusive polynomial chaos expansion to identify the key parameters for each degradation condition. We explore the reduction of battery degradation by adjusting constraints such as the maximum C-rate and voltage. Tight control of the key adjustable parameters contributes significantly to reducing the confidence interval of the degradation factors, allowing reduced charging time with minimal degradation. The application of our approach to two state-dependent fast charging protocols for a LiC6/LiCoO2 battery indicates the value in explicitly accounting for uncertainties when designing charging protocols that minimize degradation.
Shum et al
Residual water in molten CaCl2 reacts to form different byproducts, such as HCl, which can impact the corrosivity of the salt and efficiency of electrochemical operations, such as electrolytic oxide reduction and electrorefining. The ability to detect and quantify these byproducts electrochemically can provide feedback on the efficacy of vacuum drying and other purification methods, as well as the impact of these byproducts on process operations. An electrochemical signal's association with the production of H2 is verified and characterized using cyclic voltammetry (CV) and residual gas analysis. CV estimated a 2-electron exchange process associated with H2 production. CV detected trace quantities of an oxidized species containing hydrogen in the salt on the order of 10 ppm. Different salt handling methods were compared for their impact on the hydrogen electrochemical signal. It was found that 30 minutes of exposure of CaCl2 in a beaker to low-humidity air (<20%) had minimal impact on the H2 production signal.
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Alexander Karger et al 2024 J. Electrochem. Soc.
Degradation models are important tools for understanding and mitigating lithium-ion battery aging, yet a universal model that can predict degradation under all operating conditions remains elusive. One challenge is the coupled influence of calendar and cycle aging phases on degradation mechanisms, such as solid electrolyte interphase (SEI) formation. In this work, we identify and systematically compare three different SEI interaction theories found in the literature, and apply them to experimental degradation data from a commercial lithium-ion cell. In a step-by-step process, and after careful data selection, we show that SEI delamination without any cracking of the active particles, and SEI microcracking, where cycling only affects SEI growth during the cycle itself, are both unlikely candidates. Instead, the results indicate that upon cycling, both the SEI and the active particle crack, and we provide a simple, 4-parameter equation that can predict the particle crack rate. Contrary to the widely-accepted Paris' law, the particle crack rate decreases with increasing cycles, potentially due to changing intercalation dynamics resulting from the increasing surface-to-volume ratio of the active particles. The proposed model predicts SEI formation accurately at different storage conditions, while simply adding the degradation from pure calendar and cycle aging underestimates the total degradation.
KyuJung Jun et al 2024 J. Electrochem. Soc.
It is desirable to develop solid electrolytes that have both excellent reductive stability against lithium metal and oxidative stability against high-voltage cathodes. However, no inorganic superionic conductors reported thus far satisfy these criteria. Nitrides exhibit intrinsically superior stability against reduction but are often readily oxidized at voltages as low as 0.6 V. In this article, we investigated all nitride-based compounds to search for materials with improved oxidative stabilities over 2.0 V while retaining their intrinsic stability against Li metal. We found two compounds, LiPN2 and Li2CN2, with high oxidative stability > 2.0 V and low vacancy migration energies. Using fine-tuned CHGNet machine-learning interatomic potential, we found that upon introducing aliovalent dopants to introduce vacancies in Li2CN2, the dopant and vacancy strongly anchor with each other to result in trapped vacancies, which lowers ionic conductivity. In contrast, vacancies and dopants have minimal interactions in LiPN2, resulting in a high ionic conductivity. These two compounds were synthesized, but their ionic conductivities were not successfully measured because of the challenges in densification. With improved processing conditions, these compounds may serve as anode-side separators in dual-separator-type all-solid-state batteries or anode buffer layer materials interfaced with lithium metal.
Christoph Paul Schmidt et al 2024 J. Electrochem. Soc.
A novel approach is presented to model delamination and recontacting at internal interfaces of three-dimensional resolved microstructures of solid-state batteries. To resolve the effect of delaminations, we incorporate the consistent enforcement of contact constraints at those interfaces using Nitsche's method. The model incorporates charge, mass, and momentum conservation to consider electrochemistry, solid mechanics, and their interaction. After introducing and verifying the model, we examine various scenarios to quantify the effect of delaminations at the electrode-solid electrolyte interface on cell performance. The simulations show that increased mechanical prestress mitigates delamination tendencies at the electrode-solid electrolyte interface. Consistent with existing literature, the simulations demonstrate that delaminations increase the internal resistance and reduce the amount of transferred charge. In contrast to experimental analyses, the presented model allows quantitative and in-depth investigations of delamination effects. Furthermore, our analysis of two cell concepts - one assembled in the discharged state and another assembled in the charged state - indicates that cells assembled in the discharged state show a higher delamination risk at the electrode-solid electrolyte interface. The study highlights the critical relationship between solid mechanics and electrochemistry in consideration of delamination phenomena in solid-state batteries, offering valuable insights for optimizing battery design and performance.
Minsu Kim et al 2024 J. Electrochem. Soc.
Safety and maintaining high performance are key considerations during the operation of lithium-ion batteries. Battery degradation, in particular lithium plating and loss of active material, is often accelerated by fast charging. This study explores a strategy for the design of fast charging protocols that takes into account the influence of the variability between battery cells on factors that can impact degradation. We employ a non-intrusive polynomial chaos expansion to identify the key parameters for each degradation condition. We explore the reduction of battery degradation by adjusting constraints such as the maximum C-rate and voltage. Tight control of the key adjustable parameters contributes significantly to reducing the confidence interval of the degradation factors, allowing reduced charging time with minimal degradation. The application of our approach to two state-dependent fast charging protocols for a LiC6/LiCoO2 battery indicates the value in explicitly accounting for uncertainties when designing charging protocols that minimize degradation.
Timothy Lichtenstein et al 2024 J. Electrochem. Soc.
Alternatives to the widely-used standard anodic decomposition reference electrodes in molten salts are necessary to enable more easily reproduced thermochemical and electrochemical data in molten salt electrolytes. The class of standard reference electrodes called cathodic decomposition electrodes (CDEs) are easily constructed and can be used to make thermochemical measurements in molten salts more directly compared to anodic decomposition electrodes. The lithium eutectic electrode (LEE) was chosen as a sample test case for validation and was applied to thermochemical measurements of electroactive species in molten LiCl-KCl eutectic. Transient measurements were made to measure the Li+/Li reduction potential at zero current in pure LiCl-KCl eutectic relative to a Li-alloy reference electrode to validate the reference potential of the LEE. Literature-reported electromotive force measurements against Li-alloy reference electrodes were used to generate a relationship between the LEE and the standard chlorine electrode and this relationship was used to evaluate measured and reported formal potential measurements for the LiCl-KCl-GdCl3 system. This work demonstrates the general framework for defining CDEs for any molten salt system and a method for calibrating external reference electrodes against a CDE standard reference electrode, improving the ease of obtaining thermochemical and electrochemical measurements in any molten salt system.
Jia Zhang et al 2024 J. Electrochem. Soc.
Group IVA elements have aroused attention in sodium-ion batteries (SIBs) due to their Na-storage capability. Among them, Pb is less explored perhaps due to its perceived risks, but its long-standing success in Pb-acid batteries should not be neglected. Together with the well-established recycling procedures, the merits of Pb warrant further investigations as a practical SIB anode. In this work, four intermetallic phases are detected during electrochemical sodiation of Pb, which yields a capacity of ~460 mAh·g-1 (~1167 mAh·L-1) upon the formation of Na15Pb4. When pursuing full capacities, the electrode stops functioning after only 3-4 cycles largely due to electrode physical damage. The reversibility of each phase transformation pair is then assessed to explore the origins of capacity fading. The NaPb/Na9Pb4 transformation shows the worst stability, consistent with the observed structural damage (e.g., cracks and voids). Through bypassing the problematic phase transformations using a partial cycling protocol, the stability of Pb foil anodes is improved, giving 20 cycles with 85% capacity retention. Considering other factors are unoptimized, it is suggested that the Pb-based anodes should not be fully eliminated from the future roadmap of SIBs, as the prospective merits can create value to ensure the management of such materials of concern.
T. K. van Leeuwen et al 2024 J. Electrochem. Soc. 171 091501
This study is part of a series with the objective of improving fundamental understanding of reactive condensation of Chromium (Cr) vapors, which are generated from Cr containing alloys used in many high-temperature (>500 °C) process environments and can form potentially problematic condensed hexavalent (Cr(VI)) species downstream. This study specifically focuses on the effects of alkaline oxide additives in aluminosilicate fibers on Cr condensation and speciation. Cr vapors were generated by flowing high-temperature (800 °C) air containing 3% water vapor over chromia (Cr2O3) powder, with aluminosilicate fiber samples positioned downstream where the temperature decreases (<500 °C). Total condensed Cr and ratios of oxidation states were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES) and diphenyl carbazide (DPC) colorimetric/direct UV–vis spectrophotometric analyses. Results indicate presence of hexavalent Cr (Cr(VI)) species condensed on all samples investigated. The ratio of Cr(VI) to total Cr detected was consistently higher on aluminosilicate fiber samples containing alkaline oxide (CaO and MgO) additions. Computational thermodynamic equilibrium modelling corroborated experimental results showing stabilities of Ca and Mg chromate (Cr(VI)) compounds. Comparative results and analyses are presented and discussed to help inform mechanistic understanding and future related research and engineering efforts.
Highlights
Study focuses on Cr vapors generated in high-temperature environments.
Generated Cr vapors interact with ceramic insulating surfaces downstream.
Experiment designed to simulate service environment temperature and humidity.
Resulting condensed Cr species are studied as a function of fiber alkaline content.
Total Cr and Cr(VI) formed increase as alkaline content of fibers increase.
Ruozhu Feng et al 2024 J. Electrochem. Soc. 171 090501
Redox flow battery shows promise for grid-scale energy storage. Aqueous organic redox flow batteries are particularly popular due to their potentially low material cost and safe water-based electrolyte. Commonly, redox active molecules used in this field feature aromatic rings, and increasing π-aromatic conjugation has been a popular strategy to achieve high energy density, high power density, and reduced crossover in new material design. However, this approach can inadvertently hinder redox activity depending on redox mechanism. This study reveals the underlying π-π stacking effect in extended aromatic redox active compounds, where aromatic radical intermediates are involved in the redox process. We report a molecular design strategy to mitigate the negative effect of π-π stacking by altering solvation dynamics and introducing molecular steric hindrance.
Matthieu Dubarry and David Beck 2024 J. Electrochem. Soc. 171 080541
Commercial Na-ion batteries are becoming available with performance forecasted to be similar to that of their lithium counterparts. On the many diagnosis and prognosis techniques developed to characterize batteries in the past four decades, it is essential to assess how many could be directly transferred to Na-ion batteries. In particular, the degradation modes approach is among the most interesting to test because it is widely used and allows to forecast the voltage response of the cells upon degradation. This work investigates the applicability of this approach to a commercial Na-ion cell comprising hard carbon and sodium vanado-fluorophosphate electrodes.
Highlights
Commercial HC/NVPF cell incremental capacity and differential voltage signatures,
Emulation of a commercial HC/NVPF Na-ion cell from harvested half-cell data,
Forecast of the degradation modes evolution,
Xin Li et al 2024 J. Electrochem. Soc.
An accurate estimation of the lithium battery's state of charge (SOC) is critical. The article proposes a dual fractional order multi-innovations cubature Kalman filter (DFOMICKF) algorithm for estimating lithium battery SOC. The algorithm adopts the idea of multiple time scales, where one of the FOMICKF is used to identify the circuit model parameters online in the macro time scale. Another FOMICKF is used to estimate the SOC in the micro time scale, and the circuit parameters updated online in real-time are passed into the estimation of the SOC filter to form an online joint estimation method of SOC and circuit parameters. Finally, multiple algorithms of DFOMICKF, FOMICKF, FOCKF, and CKF are compared and experimented under different working conditions to compare and analyze the estimated SOC errors. It is verified that the proposed algorithm can solve the problems of inaccuracy, poor convergence, and poor robustness of the traditional Kalman filtering algorithm for estimating SOC, which has good research value.